Method and electrolytic cell to produce alkyl lead compounds from grignard solution and lead

ABSTRACT

ELECTROLYTIC CELL FOR PRODUCING ORGANO METALLIC COMPOUNDS BY ELECTROLYZING A LIQUID ELECTROLYTE IN THE PRESENCE OF A PARTICULATE CONSUMABLE METAL, WHEREIN THE CELL INCLUDES A VESSEL OF ELECTRICALLY CONDICTIVE MATERIAL, A PLURALITY OF CATHODE ASSEMBLIES MOUNTED WITHIN THE VESSEL IN A BED OF ELECTRICALLY CONDUCTIVE PARTICULATE CONSUMABLE MATERIAL, AND EACH CATHODE ASSEMBLY HAVING A CATHODE OF ELECTRICALLY CONDUCTIVE MATERIAL INSULATIVELY MOUNTED WITH RESPECT TO THE VESSEL AND A SHEATH OF LIQUID-POROUS INSULATING MATERIAL ENCLOSING THE CATHODE, AND EACH CATHODE BEING INDIVIDUALLY FUSED.

March 30, E971 G. E. BLACKMAR 3,573,178

OCE ALKYL LEAD UNDS FROM GRIGNARD SOLUTION AND LEAD METHOD AND ELECTROLYTIC CELL TO PROD COMPO 24, 1968 2 Sheets-Sheet 1 Filed Oct.

FIG.|

FIG

INVENTOR GUY E, BLACKMAR ATTYS.

March 30,1971 @,E, BLAMMAR 3,573,178

METHOD AND ELECTROLYTIC CELL TO PRODUCE ALKYL LEAD COMPOUNDS FROM GRIGNARD SOLUTION AND LEAD Filed OCT.. 24, 1968 2 Sheets-Sheet 2 INVENTOR GUY E. BLACKMR United States Patent O METHOD AND ELECTROLYTIC lCELL TO PRO- DUCE ALKYL LEAD COMPOUNDS FROM GRIGNARD SOLUTION AND LEAD Guy E. Blackmar, Freeport, Tex., assgnor to Nalco Chemical Company, Chicago, Ill. Filed Oct. 24, 1968, Ser. No. 770,370 Int. Cl. B01k 3/00; C22d 1/02 U.S. Cl. 204--59 20 Claims ABSTRACT OF THE DISCLOSURE This invention relates in general to an electrolytic cell for producing organo metallic compounds from an electrolyte and a consumable metal, and more particularly to au electrolytic cell for producing alkyl metal compounds, and still more particularly to an electric cell for producing alkyl lead compounds from Grignard solution and lead.

The present invention is particularly concerned with a new and improved electrolytic or electrochemical cell employed for the manufacture of organo metallic compounds, and in particular alkyl lead compounds, such as tetraethyl lead, tetramethyl lead, triethylrnonomethyl, diethyldimethyl lead, monoethyltrimethyl lead and mixtures thereof. In the production of alkyl lead compounds, lead particles such as lead shot are employed as a consumable anodic material, while Grignard solution cornprises the electrolyte. The anodic material is consumed by the electrolytic process. In this respect, the anodic material constitutes a sacrificial anode, as defined in United States Patent 3,287,249, in that it erodes or dissolves during the electrolytic process.

Capacity or production of an electrolytic cell, especially of the type like that of the present invention for producing organo metallic compounds, is dependent largely upon the current density established within the cell during electrolysis, which is defined as the amperes used per square foot of electrode or reaction surface. The higher the current density, the higher or greater the production capability. The amount of reaction surface available depends on the surface area of the cathodes that coact with the anodic material during the electrolyzing of the electrolyte. It will, therefore, be recognized that a cell of a given size that can produce more than another cell would be desired. Moreover, economic capacity or production over a period of time is further dependent upon the onstream time of a cell. When a cell is shut down for repair or overhaul, no production can be obtained. Accordingly, reduction of maintenance and downtime provides a net increase in capacity or production, thereby enabling more economic operation.

Heretofore, electrolytic cells, such as that shown in U.S. Patent 3,287,249 and hereinafter referred to as the prior art cell, have been employed for producing organo metallic compounds. This cell employs hollow cylindrical cathodes within which the anodic material is arranged and an electrolyte is introduced to produce the rice electrolytic reaction during application of a negative potential to the cathodes and a positive potential to the anodic material.

The cell of the present invention comprises a closed vessel of electrically-conductive material, such as steel, a plurality of cathode assemblies mounted within the vessel, and a bed of electrically-conductive particulate material Within the vessel and in surrounding relation to the cathode assemblies. Each cathode assembly includes a cathode of electrically-conductive, non-consumable material7 such as steel, and an outer membrane of berglass cloth and wire. The `cathode is arranged in an upright position within the vessel and supported thereby, but in insulating relationship thereto. The membrane includes woven wire of electrically-conductive material over the exterior surface of the cathode, and a fiberglass cloth sheath over the wire. The wire increases the current capacity of the cathode and functions as a spacer between the cathode and the fiberglass cloth sheath. In order to function as desired, the fiberglass cloth is liquid porous to permit the passage of a liquid electrolyte, but of such porosity as to prevent the passage of the particulate material. Further, the fiberglass cloth electrically insulates the particulate material from the wire and the cathode. Preferably, the cathodes are rectangular in cross-sectional shape and solid, but they may be rectangular and hollow or oval and hollow. Where the cathode might be hollow, it may have holes spaced therealong, so that the electrolyte may be introduced into the hollow cathode and discharged through the holes Iinto the bed of particulate material. Also, the cathodes may be hollow for the purpose of handling a heat exchange media.

Since the present invention is especially concerned with the production of alkyl lead compounds, the bed of particulate material is lead and the electrolyte circulated therethrough is Grignard solution. Inasmuch as the lead bed constitutes a high resistance to the ow of the Grignard solution therethrough, the wire spacer between the cathode and fiberglass sheath functions to define an electrolyte ow path along the cathode. Each cathode is individually fused, so that breakdown of the insulating fiberglass sheath and shorting of a cathode only causes removal of that shorted cathode from operation during the electrolytic process.

As will be more evident hereinafter, the electrolytic cell of the present invention provides a greatly increased production or capacity at a much lower cost relative to the prior art cell, because it is capable of a much higher current density, lower power requirements, and is capable of being maintained onstream for a much longer period of time before needing to be shut down and overhauled.

The cathodes of the prior art cell are electrically connected together, whereby the shorting out of one cathode necessitates shutdown of the entire cell for repair and/ or overhauling. The electrolytic cell of the present invention includes a construction enabling each cathode to be electrically insulated from the vessel and accordingly from each other, so that they may Ibe individually fused, whereby shorting out of any one or more cathodes causes the fuse or fuses related thereto to open and only disable the shorted out cathodes, thereby leaving the other cathodes in operation and not materially disturbing the overall operation of the cell. This enables the onstream time of the cell to be much longer than that of the prior art cell, thereby reducing the cost of maintenance and the overall cost of production of the organo metallic compound produced by the cell.

In the prior art cell, the hollow cathodes are cylindrical in shape. The cathodes in the cell of the present invention are preferably rectangular in shape enabling a greater square foot reaction surface to be provided over the cathode arrangement of the prior art cell. It is well recognized that the surface area of a rectangular in cross section object relative to a comparably sized, Cylindrical in cross section object is greater.

For the given size of a vessel it is possible to substantially increase, nearly double, the number of cathodes of rectangular shape over those of cylindrical shape, as in the prior art cell, and to thereby increase the reaction area or cathode plate surface area to enable a substantially higher, nearly double current density. More amperes per unit area of electrodes can be forced through the cell of the present invention. Further, since the same current is distributed over a larger conducting area, a lower voltage is required resulting in substantial power savings. Thus, the cell of the present invention has an output susbtantially greater than that of the prior art cell, when considering the use of vessels of the same size.

The construction of the prior art cell, when all of the cathodes are electrically interconnected, requires the necessity of having insulated spacers at both ends of the cathodes interconnected with the end closure members by bolts having special insulating construction to insulate the cathodes from the end closure members. The cell of the present invention eliminates this special construction by eliminating the need for insulating spacer plates and special bolts, thereby decreasing the cost of construction of the cell.

Accordingly, it is an object of the present invention to provide a new and improved electrolytic cell for producing organo metallic compounds.

Another object of this invention is in the provision of an electrolytic cell for making organo metallic compounds that is constructed more inexpensively than heretofore known cells, and which is capable of having a substantially greater-on-stream life, thereby reducing maintenance costs and loss production prots.

Still another object of this invention resides in the provision of an electrolytic cell for producing organo metallic compounds, wherein each cathodic element is individually fused, so that shorting of one element does` not require shutting down the entire cell and reconditioning same.

A further object of this invention is to provide an electrolytic cell for making organo metallic compounds that for a given size is capable of having a high current density, which increases production yields, while reducing operating electrical power.

Stil a further object of this invention is in the provision of an electrolytic cell for making organo metallic compounds, `which includes cathodic elements having a substantially greater electrical reaction surface area for the size of the unit relative to heretofore known cells, and wherein the amount of volume used by the cathodic elements is reduced over heretofore known cells.

Other objects, features and advantages of the invention will be apparent from the following detailed disclosure, taken in conjunction with the accompanying sheets of drawings, wherein like reference numerals refer to like parts, in which:

FIG. l is a perspective view of an electrolytic cell according to the present invention with some parts broken a-way and some parts shown diagrammatically for purposes of clarity;

FIG. 2 is an enlarged, detailed, sectional view taken substantially along line 2-2 of FIG. 1 and illustrating the mounting of a cathode assembly within the vessel of the cell;

FIG. 3 is an enlarged, transverse, sectional view of a cathode assembly and taken substantially along line 3-3 of FIG. 1;

FIG. 4 is a perspective view of a screen assembly employed at the bottom end of the cell for preventing the loss of particulate material, but permitting the flow of a liquid electrolyte;

FIG. 5 is a sectional View taken substantially along line 5 5 of FIG. 4;

FIG. 6 is a transverse, sectional view of a modified cathode assembly according to the invention;

FIG. 7 is an elevational view of the modified cathode employed in the cathode assembly of FIG. 6, with some parts broken away and other parts in section for purposes of clarity; and

FIG. 8 is a transverse, sectional view of a still further modified cathode assembly according to the present invention.

Referring now to the drawings, and particularly to FIG. l, the electrolytic cell of the present invention includes a vessel' 1f!1 of electrically conductive material, such as stell, that is sectional and includes a cylindrical shell 11, a cover member 12, and a bottom closure member 13. The shell 11 may take any other form, such as a polygonal shape, if so desired. A plurality of cathode assemblies 14 are mounted within the vessel 10 and submerged in a bed of particulate material 15. A liquid electrolyte is introduced into the vessel and circulated through the bed, while an electrical potential is applied to the cell to electrolyze the electrolyte that causes a consumption of the particulate material and the production of an organo metallic compound.

The shell 11 of the vessel is flanged at its upper end at 16 and at its lower end at 17 to facilitate the connection between the cover member and bottom closure member. The cover member 12 is in the form of a circular disc that is provided with a plurality of bolt holes that would mate with bolt holes on the flange 16` for receiving a plurality of bolts 18, that would serve to tightly secure the member to the upper end of the cylindrical shell in a liquid-tight manner. If necessary, a sealing gasket could be provided between the flange 16 and the cover member. It should be noted here that it is not necessary to electrically insulate the cover member from the shell 11. A pipe fitting 19 is suitably secured to the cover member such as by welding and in alignment with an opening 20 that may serve as the inlet or outlet for the cell during the movement of an electrolyte through the cell. This opening may also serve to permit the introduction of the particulate material 15 into the reaction chamber of the vessel. The upper end of the pipe fitting 19 is flanged at 21 to facilitate its connection to other piping.

The lower closure member 13 is conically formed with the small end extending downwardly and a large end arranged adjacent the lower end of the cylindrical shell 11. A flange 22 is provided at the upper end of the closure member l?,` and bolt holes therein aligning with bolt holes formed in the shell flange 17 permit the use of bolts 25 for interconnecting the bottom closure member with the shell in a liquid-tight fashion. Again, a sealing gasket may be provided if needed, and it is not necessary to insulate the closure member from the shell. In fact, it is necessary that electrical contact be maintained therebetween. The lower end of the bottom closure member is provided with a flange 24 that defines an opening 25 for enabling the introduction or removal of electrolyte within the vessel. Depending upon the desired flow of electrolyte through the vessel, the openings 20 and 25 will function as inlets or outlets.

The particulate material 15 would be of the type needed to perform the desired electrolytic action and to produce the desired organo metallic compound, and for producing an alkyl lead compound, the material would constitute lead of nearly pure consistency. For example, the particulate material, as lead, would be in the form of lead shot, where the particles would be any shape, such as pear-shaped, spherically-shaped or cylindrically-shaped. It will be recognized that the particulate material becomes anodic during the electrolytic reaction and is consumable to introduce lead into the electrolyte.

inasmuch as the particulate material will be of substantial weight and will be small in size, it is necessary to provide a suitable barrier at the lower end of the cell to prevent the falling out of the material. One such barrier is illustrated as a screen unit 26, which would fit between the lower end closure ange 24 and a ange 27 of a pipe 28. As seen most clearly in FIGS. 4 and `5, the screen unit 2-6 includes a ring 29 `supporting in any suitable manner a ne mesh screen 30` and a heavy-duty coarse mesh screen 31. The ring 29, and the adjacent flanges 24 and 27 are provided with aligned bolt holes for receiving connecting bolts 32 that secure the end closure member 13, screen unit 26 and pipe 28 together in fluid-type relationship. The fine mesh screen 30` faces the bed of particulate material 15 and serves to prevent the particles from passing therethrough, while allowing the liquid electrolyte to pass therethrough. Because of the great weight of the bed of particulate material, the heavy-duty, coarse screen 31 is provided for supporting the fine mesh screen 30 and the weight of the bed of particulate material.

While only a small number of cathode assemblies 14 are illustrated in the embodiment in the drawings as being mounted within the vessel 10, it will be appreciated that in a commercial installation, a large number of the cathode assemblies will be provided. For example, nearly twice as many cathode assemblies of the type illustrated in the embodiment of FIG. l would be employed in a vessel of the size that would carry a predetermined number of cathodes like that of the prior art cell. Accordingly, a much greater plate surface area and current density capacity would be realized from the cell of the present invention, and this is achieved by virtue of the crosssectional shape of the cathode assemblies, which permits a greater number of assemblies having the maximum plate surface in a given volume. Each of the cathode assemblies 14 include a cathode 33I of rectangular cross section that is solid, and which would extend in an upright position within the vessel 10 and in suspended relation relative to the cover member 12. Hanging of the cathode from the cover member is accomplished by providing a stud 34 suitably secured to the upper end of the cathode and extending upwardly through a hole 35 formed in the cover member.

Inasmuch as it is necessary that the cathode be cornpletely electrically insulated from the vessel and cover member, insulating means is provided which includes an insulating washer 36 on the stud 34 and arranged between the cover member and the cathode. The hole 35 is made larger than the stud 34 to accommodate an insulating sleeve 37, which includes a cylindrical portion 38 enclosing the stud 34 and extending the full length of the hole 35, and a ange 39, which overlies the upper surface of the cover member and effectively insulates a nut 40 from the cover member as it is drawn down onto the stud 34. The insulating washer 36 and insulating sleeve 37 may be made of any suitable insulating material that will provide the necessary electrical insulation characteristics and also be inert to the materials ernployed in the electrolytic process. Further, these insulating members are preferably formed to provide a fluidtight connection between the cathode stud 34 and the cover member 12, when the cathode is properly mounted. Any other type of insulation arrangement may be employed.

In surrounding and contacting relation with the cathode 33, a wire member 41 in the form of a screen is provided, and which is enclosed by a sheath 42 of insulating material. The wire member 41 may be of nonconducting material, but preferably is of electrically conducting material, such as steel, which will carry current and thereby increase the current capacity of the cathode 33. In the illustrated embodiment, the wire member 41 is preferably woven in any suitable fashion, such as in the shape of the well known chain link fence, which is provided with diagonal weaving. The wire member 41 effectively spaces the sheath 42 from the cathode 33 and defines an electrolyte flow path along the exterior surface of the cathode 33. Since the bed of particulate material offers a high resistance to the ow of electrolyte. it will tend to ow along this flow path where the resistance is lower.

It will be appreciated that the insulating sleeve 42 may be of any desirable material that will effectively electrically insulate the particulate material from the wire member 41 and the cathode 33, and yet be porous to the extent that it allows passage of the liquid electrolyte therethrough, but prohibits passage of the particulate material. Moreover, the insulating sheath must be inert to the elements of and the electrolytic process. Further, it is preferable that the insulating sheath be heat resistant, since the temperature of the electrolyte during electrolysis may be rather high. A suitable material is fiberglass cloth. Thus, the wire member 41 and the insulating sheath 42 define a membrane over the cathode 33 and all of which make up the cathode assembly. It will be appreciated that the membrane is provided over all of the surfaces of the cathode that are within the vessel, as it is absolutely necessary that the wire member on the cathode be insulated from the particulate material 15 to prevent shorting.

While the cathode assemblies are shown to be rectangular with one cross-sectional dimension much longer than the other and the longer dimension being radially arranged relative to the vessel, it should be appreciated that the assemblies may be arranged in any desirable manner within the vessel and in a manner to best utilize the reaction chamber for providing the greatest amount of plate surface area. In a commercial installation, the cathode assemblies would be in close, side-by-side relation, while allowing the presence of particulate material therebetween; and in a large installation, a number of concentrically-arranged rows of cathode assemblies will be provided to fill the reaction chamber. If it should be necessary, a spacer member could be provided at the lower ends of the cathodes assemblies to inhibit movement and maintain the spaced relationship at all times during the electrolytic process.

In the operation of the electrolytic cell according to the present invention, following assembly of the vessel with the assembly of the cathode assemblies and placing of same within the vessel, the reaction chamber is then filled with the particulate material such as lead shot by introducing same through the opening 20, or some other suitable opening. The lead shot fills the entire open area within the bottom closure member 13 and completely surrounds each of the cathode assemblies 14 to intimately engage against the insulating sheaths, as well as against the inner walls of the vessel. The liquid electrolyte, such as Grignard solution, is then introduced into one of the openings, such as the opening 25 to be circulated through the bed of lead shot and around the cathode assemblies. A positive DC potential is applied to the vessel in any suitable manner, which, of course, transmits the potential t0 the lead shot 15 so that together they define the anode of the cell. In FIG. l, a plurality of plates or lugs 43 are provided on the bottom closure member 13 for the purpose of connecting wires 44 thereto, which would be connected to a suitable DC positive potential. It should be appreciated that the positive potential could likewise be applied to the cylindrical shell 11 or the cover member 12, :inasmuch as they are in electrical contact with the bottom closure member 13. A negative potential is applied through wires 45 to the studs 34 of the cathodes 33, thereby applying a negative potential to the cathodes 33. The `Grignard solution is thus electrolyzed and the electrolyzed liquid is removed from the vessel, such as through the opening 20. The cathodes 33, being of steel, are essentially non-consumable, while the anodic material 15 is consumable and will erode or dissolve during the electrolytic process.

Should the insulating sheath 42 on any one or more of the cathode assemblies 14 rupture or fail to insulate the lead particles from the wire member 41 and/or the cathode 33, that cathode assembly will short out and thereafter be disabled. In order to prevent the` breakdown of the entire cell upon the shorting out of one or more cathode assemblies, each cathode is individually yfused by fuses 46. Thus, shorting out of any one or more cathode assemblies will cause opening of those fuses and disabling of those cathode assemblies, but such will not disturb the operation of the other cathode assemblies or materially affect the production of the cell. Longer onstream life is thereby achieved before it is necessary to shut down the cell and overhaul or repair same. Accordingly, fusing of each cathode prevents serious damage to the overall cell when a short occurs within a cathode.

Another form of cathode assembly is shown in FIGS. 6 and 7, wherein the cathode is generally designated by the numeral 14A and includes a hollow, rectangular-incross-section cathode 50 enclosed by a membrane defined by a wire member 51 and an insulating sheath 52. The wire member 51 and insulating sheath 52 are identical to and function the same as the wire member 41 and insulating sheath 42 of the cathode assembly 14, and the cathode 50 is likewise constructed of an electrically con-y ductive material, such as steel. Being hollow, the cathode 50 defines a central passageway or chamber 53 into which the liquid electrolyte may be first introduced and thereafter distributed strategically through discharge orifices 54.

As seen particularly in FIG. 7, the cathode 50 is provided with a mounting flange 55 at the upper end, while being closed by a bottom wall 56 at the lower end. An opening 57 is provided at the upper end of the cathode and the chamber 53 for the introduction of electrolyte therein. Inasmuch as the cathode is to be connected to a source of negative potential, it must be electrically insulated from the vessel and from the cover member 12. Accordingly, an insulating sleeve 58, which includes a vertical section 59 surrounding the upper end of the cathode and spacing same from the cover by being arranged in the hole 60, and having a fiange 61 that is arranged between the upper surface of the cover member and the cathode flange 55, prevents electrical contact between the cathode and the cover member and vessel. An inlet pipe 62 having a flange '63,` is aligned with the fiange end of the cathode and serves to bring electrolyte into the cathode. The flanges of the cathode and pipe, together with the flange of the insulating sleeve 59 and the cover member are provided with aligned holes for receiving bolts 64 that secure these members together. In order to insulate the bolts `64 from the cover member 12, insulating bushings 65 are provided, which surround the bolt shank and are received in the bolt holes to insulate r the shank from the cover. Flanges are. also provided on the insulating bushings to insulate the heads of' the bolts from the cover member.

The insulating sleeve 58 and the insulating bushings 65 are of a similar material as the insulating sleeves 37 and also facilitate the fluid-tight connections between the cathode and the cover member. Thus, the cathode is cornpletely insulated from the cover member and the vessel.

It will be appreciated that any number of discharge orifices 54 may be provided along the cathode 50 at any place desired, so that the liquid electrolyte will be introduced into the particulate anodic material where desired. Where the liquid electrolyte is introduced through hollow cathodes, it will be appreciated that only one of the openings shown in the bottom of FIG. 1 would be then utiliZed for the purpose of withdrawing the electrolyzed liquid and the other opening could be closed.

The general construction of the cathode assembly 14A may also be utilized for providing heat exchange media within the cathodes, but in such case, no discharge orifices would be provided, and the heat exchange media would merely be circulated through the cathodes. In this event, the electrolyte would be introduced into and removed from the vessel in the same manner as discussed relative to the embodiment of FIG, l

It should also be appreciated that the geometrical cross section of the cathode assemblies may take other forms, and such another form is illustrated in FIG. 8 with the cathode assembly 14B. This embodiment illustrates an oval-in-cross-section cathode assembly that is constructed like the cathode assemblies heretofore discussed and which includes a hollow oval-in-cross-section cathode 66 enclosed by a membrane of 'wire 67 and insulating material 68. While the cathode 66 is shown to be hollow, it could be solid if so desired, and it will be recognized that the wire 67 and the insulating sheath 68 are of the same material as that of the embodiment shown in FIG. 3. Where the cathode 66 would be provided with electrolyte discharge holes like the embodiment of FIGS. 6 and 7, it would operate the same. Also, it could be formed to handle heat exchange media as above explained.

From the foregoing, it will be appreciated that the electrolytic cell of the present invention provides a construction: that enables each cathode to be individually fused, so that shorting out of one cathode will not necessitate shutdown of the cell for repair; that achieves higher current density by the cathode configuration, thereby increasing production and reducing power needs; that defines greater cathode surface area for a unit of given size; and that eliminates the need of insulating spacer plates and special bolts, thereby reducing construction costs.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

The invention is hereby claimed as follows:

1. An electrolytic cell comprising, a vessel of electrically conducting material, a plurality of cathode assemblies mounted within said vessel, each assembly including a Cathode of electrically conductive non-consumable material, a sheath of porous electrically insulating material enclosing said cathode, and electrically-conductive means spacing the sheath from the cathode to define an electrolyte flow path, means electrically insulating said cathodes from the vessel, a particulate consumable electrically conductive material in said vessel completely surrounding each of the cathode assemblies in engagement with the sheaths thereof and in engagement with the inner Walls of the vessel to define with the vessel an anode, inlet and outlet means coacting with said flow paths for conveying an electrolyte through said vessel, and means for applying a source of negative potential to said cathodes and a positive potential to said anode thereby electrolyzing the electrolyte.

2. An electrolytic cell as defined in claim 1, and means for individually fusing each of said cathodes.

3. An electrolytic cell as defined in claim 1, wherein the cathodes are rectangular in cross section.

4. An electrolytic cell as defined in claim 3, wherein the cathodes are solid.

5. An electrolytic cell as defined in claim 3, wherein said cathodes are hollow for the passage of an electrolyte liquid therethrough, and hole means in said cathode permitting the movement of the electrolyte outwardly from the hollow center.

6. An electrolytic cell as defined in claim 5, wherein the cathodes are oval in cross section.

7. An electrolytic cell as defined in claim 1, wherein said spacing means is of an electrically conducting material.

8. An electrolytic cell as defined in claim 7, wherein said spacing means is defined by a wire screen.

9. An electrolytic cell as defined in claim 1, wherein said sheath is inert to the electrolyte and electrolytic reaction and of such porosity as to permit the passage of the electrolyte therethrough, but prohibit the passage of the particulate material.

10. An electrolytic cell as defined in claim 9, wherein said sheath is of fiberglass cloth.

11. An electrolyte cell comprising, a vessel of electrically conducting material, a plurality of elongate cathode assemblies mounted upright within said vessel, each assembly including a bar cathode of electrically conductive non-consumable material, a sheath of liquid-porous electrically insulating material enclosing said cathode and supported thereby, and means spacing the sheath from the cathode to define an electrolyte flow path along the cathode, means electrically insulating each of said cathodes from the vessel, said cathodes being adapted to be connected to a negaitve potential, a particulate consumable electrically conductive material in said vessel completely surrounding each of the cathode assemblies in engagement with the sheaths of the assemblies but electrically insulated from said cathodes and spacing means by said sheaths and in engagement and electrical Contact with the inner walls of the Vessel, said particulate material and said vessel defining an anode and being adapted to be connected to a positive potential, and openings at the upper and lower ends of said vessel for permitting the introduction of particulate material and an electrolyte and the discharge of the electrolyzed liquid, one of said openings defining an inlet and the other of said openings defining an outlet.

12. An electrolytic cell as dened in claim 11, and means for individually fusing each of said cathodes, so that shorting out of any one or more cathodes will not affect the operation ofthe other cathodes.

13. An electrolytic cell as defined in claim 12, wherein said cathode is solid and rectangular in cross section.

14. An electrolytic cell as defined in claim 13, wherein said spacing means of each cathode comprises electrically-conductive woven wire screen that is in electrical contact with the cathode thereby increasing the ampere capacity thereof.

15. An electrolytic cell as defined in claim 14, wherein said sheath is of chemically inert material and of such porosity as to prevent the passage of the particulate material or the contact thereof with the spacing means.

16. An electrolytic cell as defined in claim 15, wherein said sheath is of fiberglass cloth.

17. An electrolytic cell as defined in claim 14, and screen means at the opening in the lower end of the vessel permitting the passage of liquid, but prohibiting the passage of the particulate material.

18. The method of operating an electrolytic cell having an electrically conductive vessel `with a plurality of elongated cathode assemblies mounted therein in insulating relationship to said vessel, wherein each cathode assembly includes a solid bar cathode of electrically conductive non-consumable material and is enclosed in a sheath of porous electrically insulating material spaced therefrom to define an electrolyte fiow path along the exterior of the cathode, said method comprising the steps of loading the vessel with a particulate consumable electrically conductive material, so that the material completely surrounds and engages each of the cathode assemblies and engages the inner walls of said vessel to function therewith as an anode, introducing a liquid electrolyte into the vessel, passing the electrolyte along the flow paths between the cathodes and sheaths of each cathode assembly, electrolyzing the electrolyte by applying a negative potential to said cathodes and a positive potential to said anode, and recovering said electrolyzed liquid.

19. The method as defined in claim 18 and fusing each cathode so that shortin-g of one cathode does not affect operation of the others.

2t). The method of operating an electrolytic cell having an electrically conductive vessel with a plurality of elongated cathode assemblies mounted therein in insulating7 relationship to said vessel, wherein each cathode assembly includes a hollow bar cathode of electrically conductive non-consumable material and is provided with holes therealong and is enclosed in a sheath of porous electrically insulating material spaced therefrom to define an electrolyte flow path along the exterior of the cathode, said method comprising the steps of loading the vessel `with a particulate consumable electrically-conductive material, so that the material completely surrounds and engages each of the cathode assemblies and engages the inner walls of said vessel to function therewith as an anode, introducing a liquid electrolyte into the hollow cathodes, passing the electrolyte through the cathode holes and along the exterior of the cathode through the fiow paths between the cathodes and sheaths of each cathode assembly, electrolyzing the electrolyte by applying a negative potential to said cathodes and a positive potential to said anode, and recovering said electrolized liquid.

References Cited UNITED STATES PATENTS 3,180.81() 4/1965 Pear-ce et al. 204-59 3,287,249 1l/l966 Braithwaite et al. 204-260 3,306,836 2/1967 Ziegler et al 204-59X TA-HSUNG TUNG, Primary Examiner N. A. KAPLAN, Assistant Examiner U.S. Cl. XR. 204-72, 272, 275 

